No. Contrary to the sci-fi trope you occasionally see crop up, you could not make a sustainable human population starting from two people. The inbreeding would render everyone sterile (and probably severely physically and intellectually disabled) after just a couple generations.
The actual number in the paper is 98, and even that probably wouldn't be a very healthy population of humans. Around 600, with significant initial diversity, is the number I've seen tossed around as the minimum number for a genetically healthy population.
The world will be scary when we get to the point where we can implement an Anne Hathaway bot that's not in the uncanny valley. The world will be even more frightening when we have the beta Hathaway bots and they're still in the valley.
No, I meant actually sending a series of clones of Anne Hathaway, each of which raises another clone of Anne Hathaway until the target planet is reached. The first generation would, of course, be the actual Anne Hathaway.
That gives you step -1 of "invent general-purpose AI that can completely replace a human". If you've got that, why not just send the robots by themselves?
Why not just send rocks? The concept is the migration of the species, ie the fulfillment of genetic imperative. If you aren't interested in that, the rocks will be fine without us.
> If we would create a spacecraft right now, we could only reach about 200 km/s, which translates into 6300 years of travel. Of course technology is getting better with time and by the time a real interstellar project will be created, we can expect to have improved the duration by one order of magnitude, i.e. 630 years. This is speculative as technology as yet to be invented.
This is the dilemma that should make us really consider and possibly wait for the right technology. Otherwise it is quite possible to arrive to destination and find it populated for millennia.
Alistair Reynold's Revelation Space universe explores this, often times with sub-light travelers arriving at what they thought would be one of the largest cities in known space only to find it devastated by a plague. More relevantly, the book Chasm City, set in this universe, explores a set of generation ships competing to arrive first at an uninhabited planet.
Kim Stanley Robinson's Aurora comes to mind, as it explores similar ideas to the study. The featured generational starship suffers from a deteriorating biome due to inbreeding and loss of nutrients, and the book also explores the effects of disasters and politics on the viability of such a journey,
I think Samuel R. Delany's "I was the first to find you" dealt with that, but it had the twist that the newer explorers knew about the previous ship that was still on the way and went looking for them.
... or not. It's been at least 15 years since I read it.
In addition to the already-mentioned Chasm City... Into the Sea of Stars by William R. Forstchen comes to mind. Generational ships take off from a dying Earth. The Earth recovers and faster-than-light technology is eventually developed. The FTL ships are tasked with tracking down the generational ships.
> This is the dilemma that should make us really consider and possibly wait for the right technology
If one is thinking from a species planning perspective, the question is an interplay between the (a) development of propulsion technology and (b) propensity for our species to annihilate itself. Given (a) and (b) are intrinsically related, there is likely an elegant solution.
200 km/s seems an order of magnitude high to me for "today's technology". The Voyagers and New Horizons have an escape velocity of around 20 km/s. Isn't reaching escape velocity the metric you want here? You want to leave the solar system after all.
Parker Solar Probe his 200 km/s in orbit around the sun.
I wonder what would happen if people launching later decided to pick up the people who launched earlier. Like they’re headed towards the same destination anyway, following the same general intergalactic line. Sure finding a ship in space is like finding a needle in a vast vacuum but maybe their ships would emit enough radiation for their “scent” to be traceable. And if picking up other traveler isn’t important enough to warrant a pit stop, maybe the ships that left earlier would have valuable information for the ships who leave later on.
The problem there is that if you wait for the right technology to appear, it may never happen, because all of the effort and resources that would’ve been put into researching and manufacturing engines for interstellar ships would’ve instead been put into something else. There’s still a chance that we stumble upon the right tech anyway, but the chances are greatly reduced and even if we do, it’ll likely be far later (centuries even) than it would’ve been had we been had we actively been developing said technology.
From my perspective, it makes more sense to risk obsoleting previous missions and send ships as soon as it’s possible to do so because it’s a far better outcome than waiting for tech that never came and never sending a mission at all.
Can't wait to see perspectives on this one. I looked into this years ago and remember finding the number to be around 150-300 if you centrally plan reproduction (and no, you don't want an unequal gender distribution). Also that cheetahs experienced a population bottleneck of this magnitude and so we have some data on what it looks like.
Take that with a grain of salt, memory and amateur research are finicky.
The idea that the travelers need to be people as we know them today is a huge assumption that should be jettisoned.
As we improve medicine and merge with AI, we should expect other changes to be possible, not just brain interface changes, but also body changes. Essentially we are still a version 1.0 and the iterations to new versions haven't even started yet... but these should be well underway in the timeframe of starting voyages to other stars.
Even for Mars, much closer obviously, we should think about whether it's easier to change body types in the medium term than it would be to terraform Mars to a desirable level.
You might like the Behrooz Wolf books by Charles Sheffield. The main scifi gimmick at the core is complete bunkum, but the books do a lot of exploration of extreme adaptations of the body for various environments, including other planets and the vacuum of space.
> ...we should think about whether it's easier to change body types in the medium term than it would be to terraform Mars to a desirable level.
This could be called bioforming[0][1] and here's an abstract for a paper that suggests modifying humans, alongside modifying Mars, to speed colonization.[2]
Having a child that is bound to live their entire life on such a ship strikes me as tragic and depressing. I don't think I could personally be responsible for creating a life in that kind of environment. I'd hope we'd get the quality of life possible in space very high before we ever attempt any kind of thing like this.
It seems to me like the only reasonably ethical way to do it would be to have a small city's worth of people (a small city's worth of living space) and thus "society" rather than "crew".
But that runs into the organizational problem that a society that's lived in space for two or three generations may not want to deal with this messy, disease-ridden, gravity-encumbering planet business again.
Which brings up a much overlooked issue regarding colonization efforts: antibodies and the human immune system in general being exposed to an alien environment after generations of sterile space travel.
I think that's actually the primary problem with this idea. If all you have is a crew that can live on their ship, and they arrive at Alpha Centauri... now what? Terraforming on anything even remotely resembling a useful time frame is a massive undertaking. Literally in this case, requiring both substantial mass, and energy in enough quantities that it is reasonable to use mass-based measurements to quantify it! They're far more likely to just sidle up to an asteroid loaded with useful things and start using the local resources.
But if you're going to do that, there are useful asteroids waaay closer than the next star system over.
Interstellar colonization makes some degree of sense, but not until we're pretty far along exploiting the local system. It's not something even our great-grandchildren are actually going to do while there's so many resources here.
But, eventually, if humanity and its descendants keep growing, eventually it makes sense. And rather than cobbling together something that can just barely make it and then do nothing, by then they'll have the infrastructure to make many ships, and give them useful things that will actually be helpful at the other end. And they may even be able to build "bridges"; if space really is full of ice planets we can't see, those make fantastic bases for launching and deceleration lasers, and if you can use those, the economics suddenly start looking a lot more practical.
And I'd point out that barring a lot of very enormous coincidences, other planets aren't going to be "disease-ridden". If anything has to worry about being "disease-ridden", it's the ship they're on, not the almost-certainly sterile matter on the other end.
Yeah, this is a question that doesn't get brought up nearly enough in discussions about generation ships: is the entire concept unethical? You're condemning multiple generations currently unborn to spend their entire life in a can. And even once they get wherever they're going, it's probably going to be a barely-habitable frozen rock much less pleasant than Earth.
Kim Stanley Robinson's novel Aurora talks about a bunch of this. Robinson mentioned that he was tired of talk about generation ships avoiding the biological, social and ethical factors and just focusing on the physics and technology, when those are probably the easiest bits. Highly recommended.
This is the primary tension in “Aurora”. An explorer can choose to go out into the unknown, but can an explorer choose for the children of future generations? Especially considering that humans and the earth biosphere co-evolved. It is literally perfect. Perfect temperature, air mixture, solar radiation, bio-compatible flora and fauna etc. I’m not convinced it’s possible to create an extraterrestrial environment comparable to the one we have here.
Versus growing up in a trailer park, or an apartment building, or an igloo?
People have endured far worse conditions for generations. Humans are probably the best choice in fact, for creating and propagating small communities for generations.
There's a crucial difference though: if a child decides they don't like living in a trailer park, apartment, or igloo, they at least have the potential to change their situation and live somewhere else. (And to the extent they don't have that potential– i.e. if social mobility is declining– we call that a serious social problem that needs to be addressed)
A child on a generation ship would have no such choice: you're going to live and die on that ship whether you like it or not. And that's at the very minimum. It's pretty likely that, to be sustainable, a generation ship would dictate your profession, marriage partner and number of children as well, with no exit rights. Forcing that life on someone with no say in the matter is pretty unethical.
Again, that describes the lot of much of humanity for most of existance. To call it unethical is to claim, not being a modern liberal American is unethical.
Of course I exaggerate. But I see this as a First World Ethical Problem.
> Again, that describes the lot of much of humanity for most of existance.
Of course. But you hopefully agree that civilization has progressed since then. I do not find it ethical to force people backwards in time compared to the contemporary environment they could have.
If I forcibly teleported you back to the kind of agricultural, tribal society that existed for most of history, where leaving would be death (either by punishment or just lack of protection from the dangerous outside world), and the tribe's elders dictated most of your life decisions, would you consider that ethical? What about if I pledged to do it to your unborn children? That's what we're talking about with generation ships.
We're currently condemning our children to live in a world with melted ice caps and extinct ecosystem. Perhaps these lucky few will count their blessings.
You're looking at this completely wrong, and with over-emotional sentiment about "Station". Generational ships will have their own culture, rules, and design to facilitate humans across the galaxy.
As long as we can communicate with each other so we can understand each other's circumstances etc, we're good.
On a spaceship one can create an environment tailored to our needs. Here on Earth we are subjected to whatever society and industry in the 21st century does to our brains.
Children getting 6 hours of sleep because Facebook puts them on the spot 24 hours a day is also a tragedy.
> On a spaceship one can create an environment tailored to our needs.
That seems pretty optimistic. I think the reality would be exactly the opposite: resources are extremely limited in space and there is much less room for error, which pretty much demands an authoritarian society where individual choice has to be severely curtailed, and the environment would be constrained by the same lack of resources.
Of course, the level of technology in the ship would determine just how bad it would have to be, but I don't see any future within the next thousand years or so where you could have an environment on a generation ship anything like what we have on Earth.
1. By the time we do this aging and “natural death” will be a thing of the past.
2. You will never see an interstellar voyage that is longer than today’s lifespans. Because otherwise there would be time to build and launch a faster ship using new technologies which gets there sooner.
TLDR: "Moore concluded that a 200 year-long mission should have an initial crew of 150 – 180 people. (...) Among other results, it was found that an initial crew of 14000 – 44000 members is well-optimized to ensure healthy offspring, even in the case of a sudden disaster occurring once during the mission. According to his study, a crew of 150 people would always be on
the verge of extinction in the case of a large-scale catastrophe."
I had to go to the linked study to get the answer. If an article posits a question in the title...it should answer it in the body. Hopefully in the first paragraph.
Assuming you can cryogenically preserve sperm indefinitely, it seems like you could simply stock the ship with a large supply of frozen sperm gathered from distinct males and use this stockpile exclusively for reproductive purposes. As long as you have enough sperm samples there is no risk of inbreeding. Frozen sperm should, at any rate, consume far fewer resources than male colonists for an equivalent supply of genetic variety.
But the problem is sending people AT ALL. Not really which people you send.
The women you send there would still have the problem of potentially arriving to their destination to find it has been populated by humans for millennia. (If they arrived at all. Interstellar space is a dangerous place.)
It would be anticlimactic in the extreme to arrive to a destination to find a thriving civilization thousands of years ahead of you in terms of technical know how.
> It would be anticlimactic in the extreme to arrive to a destination to find a thriving civilization thousands of years ahead of you in terms of technical know how.
That would be extremely exciting! IMO even more exciting than finding a desolate planet. Discovering an entire unknown civilization is anti climatic? No way, it would be like discovering Atlantis! So what if they’re more advanced? We were capable and curious/brave enough to even make the trip! Keeping score would be pointless but the fact would remain that we made first contact with them, on their turf, even though they were more advanced.
Unless it was started by colonists who left years after you did but with technology orders of magnitude faster. Say the year after you leave in a colony ship with contemporary propulsion systems, wormhole travel is discovered and a second colonization effort is started thousands of years before you arrive.
(I chose wormholes specifically because it makes it more believable that you were not contacted or picked up and pulled along by the faster technology.)
aah, gotcha. Gee, you’d think in the eons they spent after settling on that new planet and sorting out their turf wars that they would have thought to maybe launch a ship with their advanced wormhole-hopping tech to collect earlier travelers who may still be traveling along that intergalactic path. If for any purpose other than studying how spending such a long time in space has affected them. But that would be too thoughtful or something.
Not sure who mentioned immediately launching a ship the day after landing, but I said sending out ships after colonizing, settling turf wars, advancing, etc. There’s no telling how advanced their ships or other tech would be at that point. How much would even 500 years do for space travel after they were already able to achieve such short-timespan intergalactic travel? I can’t fathom.
Anyways, lots of ways to skin a cat. Making wormholes may be one way, but faster space ships, or controlling gravity, or teleportation, or some other fantastical exploit we haven’t even begun to imagine may be another.
Wormholes are nice, but putting yourself through a subatomic mixer will not persuade anybody to try that.
You can try it with a conventional meat grinder at home, if you like that idea, as in "Fargo".
While a logically sound solution, the issue with this is that the second / third generation would not have committed to the trip and would want to produce their own offspring as opposed to those of someone else.
I have to imagine being born on a ship and being told that your grandparents signed you up to live and die on it for a science experiment would potentially cause a psychological aversion to wanting to follow the rules set down a generation before regarding sex and procreation.
How difficult is it to produce an artificial womb? Very difficult, would be my guess, and morally ambiguous to produce humans without parents, but is it possible?
Now granted, this technology up there is only intended for premature births, i.e. the fetus continues to grow in the artificial womb after birth. But with the technology for IVF covering the first phase of gestation, and this artificial womb covering the last phase, the gap between both appears to be shrinking. IANAD (I'm not a doctor) though, so take this with a grain of salt.
I doubt it. Kids adapt to the environment they are born into, and it's not like they would have experienced anything else, and they wouldn't know anyone else who had either, except for people in the original generation.
My first thoughts while reading this article was this exact issue. Are there any good sci-fi books or movies that explore this concept of what it might be like to be a middle generation on the way to a new solar system? You have little attachment to the original mission that your great-grandparents signed up for, and you'll never live long enough to see your destination.
Seems plausible to me that after the society and its people had adapted to living in deep space, they might end up simply never landing anywhere. Or finding a rogue planet and burrowing in because stars are too volatile and dangerous.
That's the easy part, gender is determined by the sperm.
You can select the sex of your offspring when doing IVF today [0]. You just don't produce males until you've arrived at your destination.
By the time we have the technology to actually undertake such a journey, we might be able to correct for genetic defects such that some mild inbreeding among a smaller population would not be an issue.
Interesting discussion, but not very forward-thinking on the biology side. As a simple critique, they claim that 32 crew would result in too much inbreeding, but what about IVF? There's no reason all the children have to be the full children of the crew. They could put sperm and egg cells from thousands of donors into deep freeze before leaving.
There's also no discussion of life extension, which seems more near term than interstellar starcraft.
Anyway, we will probably have good data on the optimal size of asteroid colonies long before interstellar colonization is a live issue.
This is asking the wrong question. We don’t know how to create a robust artificial biosphere, we don’t know how to shield such a large ship from radiation efficiently, we don’t know how to maintain or create the human microbiome, because we’re nowhere near understanding it. We’re so far from being able to survive off of Earth that we don’t even know all of the challenges that exist.
Even if we had the propulsion, which we don’t, we’d still be screwed.
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[ 4.5 ms ] story [ 138 ms ] threadThe actual number in the paper is 98, and even that probably wouldn't be a very healthy population of humans. Around 600, with significant initial diversity, is the number I've seen tossed around as the minimum number for a genetically healthy population.
This is the dilemma that should make us really consider and possibly wait for the right technology. Otherwise it is quite possible to arrive to destination and find it populated for millennia.
That’s 1952. Probably it was already a trope by then...
... or not. It's been at least 15 years since I read it.
If one is thinking from a species planning perspective, the question is an interplay between the (a) development of propulsion technology and (b) propensity for our species to annihilate itself. Given (a) and (b) are intrinsically related, there is likely an elegant solution.
Parker Solar Probe his 200 km/s in orbit around the sun.
From my perspective, it makes more sense to risk obsoleting previous missions and send ships as soon as it’s possible to do so because it’s a far better outcome than waiting for tech that never came and never sending a mission at all.
Take that with a grain of salt, memory and amateur research are finicky.
As we improve medicine and merge with AI, we should expect other changes to be possible, not just brain interface changes, but also body changes. Essentially we are still a version 1.0 and the iterations to new versions haven't even started yet... but these should be well underway in the timeframe of starting voyages to other stars.
Even for Mars, much closer obviously, we should think about whether it's easier to change body types in the medium term than it would be to terraform Mars to a desirable level.
This could be called bioforming[0][1] and here's an abstract for a paper that suggests modifying humans, alongside modifying Mars, to speed colonization.[2]
[0] http://memory-alpha.wikia.com/wiki/Bioforming
[1] http://terraforming.wikia.com/wiki/Bioforming
[2] https://www.researchgate.net/publication/289486325_Bioformin...
But that runs into the organizational problem that a society that's lived in space for two or three generations may not want to deal with this messy, disease-ridden, gravity-encumbering planet business again.
1. be sterile, meaning that this is not a concern. (The only germs that settlers will run into are those they brought with themselves on the ship.)
2. contain alien germs, in which case no humans would have antibodies for them regardless of origin or travel speed.
But if you're going to do that, there are useful asteroids waaay closer than the next star system over.
Interstellar colonization makes some degree of sense, but not until we're pretty far along exploiting the local system. It's not something even our great-grandchildren are actually going to do while there's so many resources here.
But, eventually, if humanity and its descendants keep growing, eventually it makes sense. And rather than cobbling together something that can just barely make it and then do nothing, by then they'll have the infrastructure to make many ships, and give them useful things that will actually be helpful at the other end. And they may even be able to build "bridges"; if space really is full of ice planets we can't see, those make fantastic bases for launching and deceleration lasers, and if you can use those, the economics suddenly start looking a lot more practical.
And I'd point out that barring a lot of very enormous coincidences, other planets aren't going to be "disease-ridden". If anything has to worry about being "disease-ridden", it's the ship they're on, not the almost-certainly sterile matter on the other end.
Kim Stanley Robinson's novel Aurora talks about a bunch of this. Robinson mentioned that he was tired of talk about generation ships avoiding the biological, social and ethical factors and just focusing on the physics and technology, when those are probably the easiest bits. Highly recommended.
I agree. That's why I'm not moving to the suburbs.
Suffice it to say the technology is not yet up to the task.
People have endured far worse conditions for generations. Humans are probably the best choice in fact, for creating and propagating small communities for generations.
A child on a generation ship would have no such choice: you're going to live and die on that ship whether you like it or not. And that's at the very minimum. It's pretty likely that, to be sustainable, a generation ship would dictate your profession, marriage partner and number of children as well, with no exit rights. Forcing that life on someone with no say in the matter is pretty unethical.
Of course I exaggerate. But I see this as a First World Ethical Problem.
Of course. But you hopefully agree that civilization has progressed since then. I do not find it ethical to force people backwards in time compared to the contemporary environment they could have.
If I forcibly teleported you back to the kind of agricultural, tribal society that existed for most of history, where leaving would be death (either by punishment or just lack of protection from the dangerous outside world), and the tribe's elders dictated most of your life decisions, would you consider that ethical? What about if I pledged to do it to your unborn children? That's what we're talking about with generation ships.
We're currently condemning our children to live in a world with melted ice caps and extinct ecosystem. Perhaps these lucky few will count their blessings.
As long as we can communicate with each other so we can understand each other's circumstances etc, we're good.
Children getting 6 hours of sleep because Facebook puts them on the spot 24 hours a day is also a tragedy.
That seems pretty optimistic. I think the reality would be exactly the opposite: resources are extremely limited in space and there is much less room for error, which pretty much demands an authoritarian society where individual choice has to be severely curtailed, and the environment would be constrained by the same lack of resources.
Of course, the level of technology in the ship would determine just how bad it would have to be, but I don't see any future within the next thousand years or so where you could have an environment on a generation ship anything like what we have on Earth.
2. You will never see an interstellar voyage that is longer than today’s lifespans. Because otherwise there would be time to build and launch a faster ship using new technologies which gets there sooner.
https://arxiv.org/ftp/arxiv/papers/1708/1708.08649.pdf
I had to go to the linked study to get the answer. If an article posits a question in the title...it should answer it in the body. Hopefully in the first paragraph.
The women you send there would still have the problem of potentially arriving to their destination to find it has been populated by humans for millennia. (If they arrived at all. Interstellar space is a dangerous place.)
It would be anticlimactic in the extreme to arrive to a destination to find a thriving civilization thousands of years ahead of you in terms of technical know how.
Right. It doesn't seem to me that humans can live outside of Earth's safety for any significant duration of time at all. The Sun is very explosive.
That would be extremely exciting! IMO even more exciting than finding a desolate planet. Discovering an entire unknown civilization is anti climatic? No way, it would be like discovering Atlantis! So what if they’re more advanced? We were capable and curious/brave enough to even make the trip! Keeping score would be pointless but the fact would remain that we made first contact with them, on their turf, even though they were more advanced.
(I chose wormholes specifically because it makes it more believable that you were not contacted or picked up and pulled along by the faster technology.)
A mission like you suggest would require us to create precisely calibrated wormholes. Which is quite a step beyond DISCOVERING a wormhole.
Anyways, lots of ways to skin a cat. Making wormholes may be one way, but faster space ships, or controlling gravity, or teleportation, or some other fantastical exploit we haven’t even begun to imagine may be another.
I have to imagine being born on a ship and being told that your grandparents signed you up to live and die on it for a science experiment would potentially cause a psychological aversion to wanting to follow the rules set down a generation before regarding sex and procreation.
Artificial wombs are already a thing: https://www.cbsnews.com/news/artificial-womb-baby-lamb-raise...
Now granted, this technology up there is only intended for premature births, i.e. the fetus continues to grow in the artificial womb after birth. But with the technology for IVF covering the first phase of gestation, and this artificial womb covering the last phase, the gap between both appears to be shrinking. IANAD (I'm not a doctor) though, so take this with a grain of salt.
[0]: https://en.wikipedia.org/wiki/Sperm_sorting
There's also no discussion of life extension, which seems more near term than interstellar starcraft.
Anyway, we will probably have good data on the optimal size of asteroid colonies long before interstellar colonization is a live issue.
So long as we’re comparing unknown unknowns, we might as well throw fusion and GAI in there.
Even if we had the propulsion, which we don’t, we’d still be screwed.
Hard times create strong men. Strong men create good times. Good times create weak men. Weak men create hard time.
This social dynamics would not go well on a generational ship.
With 32 the chances of success drop to 0%
I thought the number would be 10-50 times larger.